A rapid, sensitive enzyme-linked immunoassay for human thyrotropin

In this enzyme-linked immunoassay for human thyrotropin (TSH) in unextracted serum we use 96-well immunoenzymometric assay plates, first coated with polyclonal antibody to TSH, then incubated with the serum samples and reacted with mouse monoclonal antibody to human TSH. After incubation with alkaline phosphatase-labeled antibody against mouse IgG, disodium p-nitrophenyl phosphate is added and the color change is measured spectrophotometrically. Assay sensitivity is 0.1 milli-int. unit/L. Cross reactivity with lutropin, follitropin, or choriogonadotropin was negligible. TSH concentrations ranged from 0.4 to 4.1 milli-int. units/L in 43 normal subjects (mean 2.0, SD 1.0), and were uniformly less than 0.3 milli-int. unit/L in 23 patients with hyperthyroidism. Features which make this assay advantageous to the clinical laboratory include ease of set-up, ability to assay many samples at a time, high sensitivity, rapid turnaround time (8 h), and absence of requirements for radioactive materials.